Introduction[1]

The main goal of conventional agriculture is to maximize both production and income. Intercropping, the agricultural practice of cultivating two or more crops in the same space at the same time, is an old and commonly used cropping practice that aims to match efficiently crop demands to the available growth resources and labor. The most common advantage of intercropping is the production of greater yield on a given piece of land by making more efficient use of the available growth resources using a mixture of crops of different rooting ability, canopy structure, height, and nutrient requirements based on the complementary utilization of growth resources by the component crops. Mixed cropping of cereals with non-cereal plants, in addition to the optimal and fair use of resources such as land and labor, increased productivity per unit area and strengthened total productivity per unit area and time. In mixed cropping of bean and sesame, treatments including 25:75, 50:50 and 75:25 had 1000-seed weight, number of capsules or pods per plant, number of seeds per pod and harvest index were higher than other treatments.

Materials and Methods

An experiment was carried out as factorial based on a randomized complete block design with three replications in Gonbad Kavous University farm from 2017-to 2018. The intercropping ratios were in nine levels, including sole crop of chickpea and lettuce, replacement intercropping of 33, 50, and 66% lettuce instead of chickpea, and additive intercropping of 100% cicer + 33, 50, 67, and 100% lettuce and pure nitrogen consumption in three levels of 0, 50 and 100 Kg^-ha. Row distance was 30cm, and row lengths were 3m. The distance between plants in rows was 20 cm for lettuce and 10 cm for chickpeas. The number of rows in sole cropping of chickpea and lettuce was four, 50% lettuce + 50% chickpeas 4 (chickpea-lettuce-chickpea-lettuce), 33% lettuce + 67% chickpea 5 (chickpea-lettuce-chickpea-chickpea–lettuce), 33% chickpea + 67% lettuce 5 (lettuce-chickpea-chickpea- lettuce-chickpea) and in additive treatments was 8 (lettuce-lettuce-lettuce-lettuce-lettuce-lettuce-lettuce-lettuce-) with 15 cm from together. In additive treatments distance of plants was 60, 40, 30, and 20 cm for 33, 50, 67, and 100% increase, respectively. SAS Ver. 9.4 was performed for statistical analysis of data, and the least significant difference test (LSD) at the 5% probability level was employed for mean comparisons.

Results and Discussion

The results showed that the highest dry weight, number of pods per plant, number of seeds per plant, 1000-seed weight, seed weight per plant, and chickpea harvest index were obtained from replacement series of 33% chickpea and 67% lettuce. This was due to reduced external competition, which provided more space for the plant and produced more photosynthetic material. Also, the lowest dry weight, number of pods per plant, number of seeds per plant, seed weight per plant, and 1000-seed weight of chickpea were obtained from an increase of 100% lettuce to chickpea. With increasing nitrogen consumption, plant weight, the number of pods per plant, number of seeds per plant, seed weight per plant, 1000-seed weight and chickpea harvest index, and lettuce plant height and weight were increased. By increasing of nitrogen, plant growth, yield components, and consequently, chickpea seed yield increased.

Conclusion

Among the two pea and lettuce plants, lettuce plant weight was higher. The higher weight of lettuce can be attributed to the genetic characteristic of the plant (harvest of the whole plant and high level of water content of the plant). The weight of both species increased with increasing nitrogen consumption. The highest harvest index resulted from the treatment of 50 kg nitrogen per hectare, and the lowest harvest index was obtained from the treatment of non-consumption of nitrogen. Chickpea plant dry weight was reduced due to increasing density which in turn resulted in high competition between plants. Seed weight and yield components of chickpea decreased with increasing density.

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